Understanding,Computer,Memory, computer Understanding Computer Memory

Gone are those times when the companies and the organisations didn't need a hi-tech system to handle them. Owing to the considerable increase in the business sector and thus, an enormous increase in the complexity of the organisational struc ----------------------------------------------------------Permission is granted for the below article to forward,reprint, distribute, use for ezine, newsletter, website,offer as free bonus or part of a product for sale as longas no changes a

----------------------------------------------------------Permission is granted for the article below to forward,reprint, distribute, use for ezine, newsletter, website,offer as free bonus or part of a product for sale as longas no changes are made and the byline, copyright, and theresource box below is included.----------------------------------------------------------Understanding Computer Memory By Stephen BucaroUnderstanding computer memory is important because yourcomputer's memory is where the action is. Sure yourcomputer's central processing unit (CPU) may be thecomputer's brain, but what good is a brain without memory?Because memory is such an important part of the computer,it has been redesigned and tweaked over the years to makeit store more data and work faster. That has resulted inall kinds of technical terms and contractions. In thisarticle, I attempt to clear up some of these terms andgive you a basic understanding of computer memory.When you work with an application on your computer, it isloaded into "main memory". There are other kinds of memorybesides main memory. For example, there is "flash BIOS"memory and "cache" memory. In fact, I could argue that acomputer consists mainly of memory. Even the CPU consistsmainly of a type of memory called "registers". In thisarticle, I focus on main memory.Memory is actually an array of "cells". Each cell holdsa binary bit, either 0 or 1. The cells are arranged inrows of 32 cells to store each "word". A word mightcontain the bits to code a single number or a singlecharacter. Each word can be accessed by it's address. Acomputer does not have to access the addresses innumerical order. It can store or retrieve a word from anyaddress at random, hence the term "random access memory"(RAM).Because a computer needs millions of memory cells, theyhave to be cheap. The cheapest memory cell is an extremelytiny capacitor. In reality "0" means no electric chargeis stored in the cell and "1" means an electric charge isstored in the cell. A tiny capacitor can store an electric charge, but thatcharge dissipates off within a few milliseconds. Toprevent loss of the data, the computer uses circuitrythat repeatedly scans all the memory cells and refreshesthe charge in any cells that contain a "1". This circuitryoperates between accesses of the memory by the CPU andother components. This continuous recharging is referredto as "dynamic" refresh, hence the term "dynamic" RAM(DRAM).I am always surprised at how many people who work withcomputers don't understand what a "bus" is. It's verysimple. You need a wire to connect to a memory cell.Instead of a wire, a circuit board uses a copper "trace"inside or on the surface of the circuit board. To accessa word of data, you need 32 parallel traces. You alsoneed a few traces to carry the signals that controlwhether you are reading or writing the memory. Thisdescribes the "data bus".To access a word of data, you need to provide the addressof the word. It requires 64 parallel traces for the"address bus". There are many other parallel groups oftraces on the circuit board that conduct variouscommunication and control signals, each of them isreferred to as a "bus". The most important signal tracingaround the circuit board is the system clock.The system clock is the "heart beat" of the system. It isa continuous stream of electric pulses at a very highfrequency. If you have a 1.2 GHz computer system, thenyour system clock pulses come at a rate of 1,200,000,000per second. Memory can be accessed on the rising edge ofthe system clock. In other words, memory reading andwriting is synchronized to the system clock, hence theterm "synchronous" DRAM (SDRAM).SDRAM comes in a 168-pin dual inline memory module (DIMM)package. It comes in two speeds, 100 MHz (PC100) and 133MHz (PC133). It comes in 3.3 volt and 5.0 volt versions.Some SDRAM contain extra circuitry called "error checkingand correction" (ECC) that stores extra bits along withthe data. The extra bits are used to verify the integrityof the data and correct any errors.New systems use a type of memory that can access data onthe rising edge and the falling edge of the system clockpulses. This means your computer can access the data inmemory at double the rate, hence the term "Double DataRate SDRAM (DDR-SDRAM).DDR-SDRAM comes packaged in a 168-pin DIMM. It comes intwo speeds, 266 MHz (PC2100) and 333 MHz (PC2700). If yourmotherboard has more than one memory module slot, and youhave only one memory module, you might be required toinstall the single DIMM in slot 1.Some Intel motherboards use Rambus DRAM (RDRAM). RDRAMuses a proprietary communications channel to accessmemory. RAMBUS is packaged in a 184-pin RAMBUS In-lineMemory Module (RIMM). There are two connectors on anIntel Rambus motherboard, each must contain either a RIMMor a C-RIMM. A C-RIMM (continuity RIMM) does not containmemory. It is a module that provides a path pass-throughfor the signals.If you have an older computer, its main memory may use"fast page memory" (FPM) or "extended data output" (EDO)memory. Some of these used a special "parity bit" tovalidate the integrity of the data. These older types ofmemory came packaged in a 30 pin single inline memorymodule (SIMM) or a 72 pin SIMM.If you want to upgrade your computer's memory, make sureyou are using the correct type of memory for yourmotherboard. It's important to study the manual that camewith your motherboard to determine exactly what type andspeed of memory is required.----------------------------------------------------------Resource Box:Copyright(C)2003 Bucaro TecHelp. To learn how to maintainyour computer and use it more effectively to design a Website and make money on the Web visithttp://bucarotechelp.comTo subscribe to Bucaro TecHelp Newsletter Send a blankemail to mailto:bucarotechelp-subscribe@topica.com---------------------------------------------------------- Article Tags: Computer Memory, Main Memory, Circuit Board, System Clock, Memory Module